Gold- and Silver-Catalyzed Reactions of Propargylic Alcohols in the Presence of Protic Additives

A wide range of primary, secondary and tertiary propargylic alcohols undergo a Meyer–Schuster rearrangement to give enones at room temperature in the presence of a gold(I) catalyst and small quantities of MeOH or 4‐methoxyphenylboronic acid. The syntheses of the enone natural products isoegomaketone and daphenone were achieved using this reaction as the key step. The rearrangement of primary propargylic alcohols can readily be combined in a one‐pot procedure with the addition of a nucleophile to the resulting terminal enone, to give β‐aryl, β‐alkoxy, β‐amino or β‐sulfido ketones. Propargylic alcohols bearing an adjacent electron‐rich aryl group can also undergo silver‐catalyzed substitution of the alcohol with oxygen, nitrogen and carbon nucleophiles. This latter reaction was initially observed with a batch of gold catalyst that was probably contaminated with small quantities of silver salt. Enones made easy: Primary, secondary and tertiary propargylic alcohols undergo an efficient Au‐catalyzed Meyer–Schuster rearrangement, in the presence of protic additives. The rearrangement of primary alcohols can be combined with the addition of nucleophiles to the resulting enone to give β‐substituted ketones in a one‐pot procedure. Electron‐rich propargylic alcohols undergo Ag‐catalyzed substitution with a variety of oxygen, carbon and nitrogen nucleophiles (see scheme).